The prior art of the kind described includes an automatic door, an abnormality (advancement or ingress) alarm, a metal detector or the like which incorporate photo-sensors, a depressed plate or the like. All of these utilize either non-contact sensors or mechanical switches such as photo-sensors, microswitches, electrostatic proximity switches and electromagnetic sensors, which are operable to detect an opening or closing of an electrical contact, an interception or opening for a radio wave path, a change in the electric or magnetic field or the like which is attributable to the contact by or proximity or passage of an object or a man, thus turning an electrical device on and off, which may include a buzzer, a meter, an automatic door, a relay, a monitor television set or electromechanical controlling device.
With these arrangements, an on/off control of an electrical device cannot be achieved unless an object or a man undergoes a relatively large movement at a close distance thereof relative to a sensor. Since a sensor is incapable of detecting a change in the status of a very small part of an object or a man, it is a usual practice in the prior art to provide an entry unit which essentially comprises a key switch, in an apparatus which energizes various electrical devices. By way of example, a road vehicle is provided with various electrical devices associated with corresponding key switches, volume controls. However, it is dangerous that a driver stretches out his arm or twists his body in order to operate the switch or volume control durig the time he is driving the vehicle. In addition, a delicate operation of such switch or volume control involves difficulty since the driver cannot divert his eyes away from the forward direction and to attend to these controls carefully over a relatively long period of time. Accordingly, it is contemplated that a voice recognition apparatus be provided to control various electrical devices in response to the recognition of a voice given off by the driver. However, this arrangement is susceptible to an erroneous recognition in view of noises which prevail within the vehicle.